This thorough film explores how ‘America’s dad’ came to stand trial for sexual assault. Plus: a frank Lady Lucan reveals the sad truth of her marriage

Bill Cosby was “a great role model, a great father, a great husband, a great entertainer”, says Lynn Norment, former editor of Ebony magazine, in Bill Cosby: Fall of an American Icon (BBC 2).

TV critic James Poniewozik says he was “technically brilliant as a comedian”. And that The Cosby Show “was recognised as a social good, that people of all stripes and backgrounds and colours could identify with this family”.

It made African-Americans proud, it made white Americans feel good. “People loved him, he was America’s dad,” says Joseph C Phillips, who worked with Cosby on the programme.

Lili Bernard also worked on The Cosby Show (only once, crucially). “It was challenging that notion of blackness with wrongness, because the media has perpetuated a negative image of the black person,” she says.

So far, so yay. It could be be a biographical tribute, This Is Your Life, Bill. But then Bernard also says: “He drugged me, raped me and then he threatened serious consequences to my life.”

And Victoria Valentino describes, in sickening detail, how Cosby – whose trial for the sexual assault of another woman, Andrea Constand, has just begun – drugged and raped her in 1969.

So why all the first part, all the great role model and America’s dad, in a documentary about how he came to trial? Because it’s an essential part of the story. And not just because of the spectacular height from which he has fallen (Jennifer Lee Pryor says “Bill was the Mount Everest of celebrity”, and she should know, having been married to Richard “K2” Pryor a number of times).

This thorough film explores the story’s context that stretches back to the civil rights movement. Cosby was such a brilliant force for social good, he and his sitcom broke down racial barriers and appealed to everyone. This wasn’t just about the great wealth machine of Hollywood keeping people silent. It was about no one wanting to believe anything was wrong. “Can you believe that my trust for him as my father figure was so great,” says Bernard. “I trusted him so much I couldn’t make that connection that he could possibly do that.”

If the person being wronged didn’t believe, even as it was happening to her, it is perhaps not surprising that the US didn’t want to know either. You wouldn’t, about your dad, would you? Until you couldn’t ignore it any longer.